In the background art, for pattern exposure on a printed circuit board, a TFT substrate or a color filter substrate of a liquid crystal display or a substrate of a plasma display (hereinafter referred to as “substrate”), a mask serving as a master pattern is produced, and the substrate is exposed to light through the mask by a mask exposure apparatus.
In recent years, in spite of increasing dimensions of substrates, the time allotted to design and production of these substrates becomes shorter and shorter. When the substrates are designed, it is very difficult to eliminate design errors perfectly. Exposure is often performed with another mask produced newly on revised design. In addition, some kinds of substrates are often produced in a multi-item small-quantity production manner. The situation that a mask is produced for each of many kinds of substrates has been inevitable though it should be avoided in terms of the cost, the date of delivery, etc.
In consideration of the aforementioned situation, the request for maskless exposure using no mask is increasing in recent years. One of methods for performing maskless exposure is a method in which a two-dimensional pattern generated by use of a two-dimensional spatial modulator such as a liquid crystal or a DMD (Digital Mirror Device), and a substrate is exposed to light with the two-dimensional pattern through a projection lens (Japanese Patent Laid-Open No. 320968/1999). In addition, there is a method in which a substrate is scanned with a laser beam by use of a high-power laser and a polygon mirror and exposed to the laser beam by use of an EO modulator or an AO modulator. Thus, the substrate is patterned.
However, in the former background-art method, a comparatively fine pattern can be drawn, but the apparatus is expensive.
On the other hand, in the latter background-art method, substrates can be produced at a comparatively low cost due to a simple configuration of the apparatus, but it is difficult to pattern a large area with high definition. In addition, since a high-power laser is required in order to improve the throughput, the apparatus cost increases, and the running cost also increases.